Character mistake: Reacher asks the MP Sgt who her "DI" was in "boot camp." The Army doesn't have Drill Instructors or boot camp but rather "Drill Sergeants and Basic Training." Call a drill sergeant a DI and you'll be doing push-ups, seen it happen.
Character mistake: Jack breaks out of prison and uses Military Police Car L67. When the General discovers this he radios to all units and says S67.
Answer: Although it's technically a mistake, it is common in films to show military officers in dress uniforms with medals and ribbons to show that particular soldiers are important. A layperson may not know military uniform protocols but they can certainly tell that dress uniforms with a lot of medals signifies high rank at a glance.